No abstract

There are approximately 450 species of oaks (Quercus L., Fagaceae) and they are the dominant tree species in many ecosystems and landscapes throughout the Northern Hemisphere (Plomion et al., 2016).Classifying oak trees is challenging because of the existence of a large number of interspecific morphological characteristics and intraspecific morphological variations, partly due to hybridization and introgression, subsequently influencing the phylogenetic reconstruction of oak spe-

Quaternary salts can form semi-clathrate hydrates, caging gas molecules in the empty small cages, which have the potential for the separation of mixtures, such as the simulated flue gas [CO 2 (17 mol %)/N 2 mixtures]. To enhance the CO 2 separation from CO 2 /N 2 binary mixtures, three quaternary salts, tetra-n-butylammonium bromide (TBAB), tetra-nbutylphosphonium bromide (TBPB), and tetra-n-butylammonium nitrate (TBANO 3 ), are investigated at different operating conditions by a one-stage hydrate separation process. The results indicate that the induction time for each quaternary salt system can be shortened to less than 5 min under the optimal operating condition. Meanwhile, each quaternary salt can significantly promote the CO 2 separation under its optimal condition. TBANO 3 displays the strongest capability in terms of gas consumption and CO 2 separation with the pressure drop of 0.72 MPa and the highest split fraction of 67% and separation factor of 15.54 compared to the other two salts. Besides, CO 2 can be further removed from 17 to 7 mol % in the presence of TBANO 3 . TBPB also has a potential effect on CO 2 separation with the pressure drop of 0.57 MPa and the separation factor of 14.06. The result demonstrates that TBANO 3 and TBPB are two better additives for efficient hydrate capture of CO 2 .